The reliability of a wireless channel is a key factor influencing the performance of a wireless communication system. There are multiple methods for improving the reliability of wireless communications, which include a channel coding method with an excellent performance, a combination method of channel coding and modulation, a method utilizing both space-time coding for a diversity gain and multiple-antenna receiver diversity, and a hybrid repeated transmission method utilizing a time variation feature of a channel, and so on. In the hybrid repeated transmission method utilizing the time variation feature of the channel, signals in an error part are repeatedly transmitted in the time variation channel in different coding and mapping manners, signals to be repeatedly transmitted and signals which have been repeatedly transmitted are merged by a receiver, that is, the multiple independent signals are merged, to confront fading of the wireless channel by using a diversity, thereby improving the transmission reliability of the wireless channel.
For different wireless communication systems, different hybrid repeated transmission methods utilizing a time variation feature of a channel are used. For example, a method in which recombination is performed for each repeated transmission is used in a cellular network, so that a diversity gain in a time dimension can be obtained; whereas a simple repeated transmission is used in a wireless local area network (WLAN) system, that is, multiple repeated transmissions are performed in a same manner. The wireless channel is quasi-static, therefore, the transmission reliability can be improved with only the simple repeated transmission, and in addition, the simplicity of the wireless communication system can be ensured.
With the increasing user requirements, throughput of the wireless communication system needs to be increased. Since overhead of the transmission takes a fixed time and increasing the throughput can not reduce the time taken by the overhead, for fixed-length data packets, increased throughput may lead to decreased efficiency of a media access control (MAC) layer in the time dimension. In order to increase the throughput and keep the efficiency of the MAC unchanged, lengths of data packets in the MAC layer need to be increased by the same proportion.
Usually, the repeated transmission used by the WLAN system includes: in a case of a single user, a transmitter sends data, waits for and receives an ACK or a block ACK (BA) fed back by the receiver, and clears data in a cache after the ACK for the data is received or sends again the data which is not correctly received by the receiver; in a case of multiple users, data and a block ACK request (BAR) are sent for each of the multiple users by the transmitter, the receiver is requested to send the BA, and if the length of data packets exceeds the length of the cache, the cache overflows and an unrecoverable loss of data is caused. In the case of the multiple users, the BAR and the BA are sent for each of the multiple users, which results in high overhead and low efficiency of the MAC.